Water and nitrate budgets in a rendzina cropped with oilseed rape receiving varying amounts of fertilizer

Autor: Bruno Mary, B. Leviel, Benoit Gabrielle, Eric Justes, Ghislain Gosse
Rok vydání: 1998
Předmět:
Zdroj: European Journal of Soil Science. 49:37-51
ISSN: 1365-2389
1351-0754
Popis: Summary Pollution of the environment by nitrogen (N) has emerged as a serious concern in agriculture, especially in the case of crops such as oilseed rape. To assess the effect of N fertilization on N dynamics, the movements of water and nitrate were determined in a rendzina near Châlons-en-Champagne (eastern France) cropped with oilseed rape with three levels of fertilizer N and in a bare control. From in situ micrometeorological measurements, actual evapotranspiration rates were computed with an energy budget and used to calibrate an evapotranspiration model based on meteorological data and crop leaf area index. Water flow below 120 cm was then deduced from periodic measurements of soil moisture contents and precipitation, and the associated nitrate leaching fluxes were calculated from the NO3 concentration measured at the same depth. Denitrification rates and ammonia volatilization were monitored in the field after fertilizer applications, and crop assimilation of nitrogen was determined frequently during the growth cycle. A nitrate budget gave an approximation of the in situ net mineralization fluxes. The water balance was influenced by the crop and its fertilization: the crop's canopy and roots enhanced the water loss by evapotranspiration and contributed to diminish the soil water storage, whereas drainage volumes were about the same for all cropped treatments, and significantly greater in the bare soil. The rainy winter was particularly favourable to leaching, and losses were much greater (+ 41%) under the over-fertilized crop than under the non-fertilized one, but remained less (– 42%) than those under the bare control soil. Bilans hydriques et azotes d'une culture de colza sur rendzine avec differentes doses d'engrais Les pollutions de l'environnement par l'azote sont devenues une preoccupation majeure en agriculture, particulierement dans le cas des cultures comme le colza. Pour evaluer les effets de la fertilisation azotee sur la dynamique de l'azote, les transferts d'eau et de nitrate d'une rendzine ont ete mesures pres de Châlons-en-Champagne (Est de la France) sur des parcelles experimentales de colza avec trois niveaux de fertilisation azotee et sur une parcelle temoin en sol nu. A partir de mesures micrometeorologiques in situ, l'evapotranspiration reelle a ete calculee par bilan energetique de la surface du sol, et un modele d'evapotranspiration ayant pour entrees des donnees meteorologiques classiques et l'indice foliaire de la culture a ete calibre. Le flux net d'eau sous 120 cm a ete alors deduit de mesures periodiques de teneur en eau du sol et de precipitations, et les flux de nitrate associes ont ete calcules a partir des concentration mesurees a la meme profondeur. Les flux de denitrification et la volatilisation d'ammoniac ont ete mesures au champ apres les apports d'engrais; l'absorption d'azote par la culture a ete determinee frequemment pendant le cycle de croissance. Enfin, un bilan azote a donne l'ordre de grandeur de la mineralisation nette. Le bilan hydrique a ete influence par la culture et sa fertilisation: le couvert vegetal et les racines ont accentue les pertes d'eau par evapotranspiration et par consequent le stock d'eau, tandis que la lame d'eau drainee etait a peu pres la meme pour tous les traitements cultives, et significativement plus elevee pour le sol nu. L'hiver particulierement pluvieux a ete tres favorable au lessivage, et les pertes ont ete beaucoup plus fortes (+ 41%) sous la culture sur-fertilisee que sur la culture non-fertilisee, mais elles sont restees inferieures (– 42%) a celles sous sol nu. Nomenclature
Databáze: OpenAIRE
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